The present invention relates to optical fiber technology, and more particularly, to an adapter for holding and connecting the end of a fiber to test equipment and to a fixture for positioning the fiber end in a desired relation to the adapter; the invention also relates to the method of cooperative use of an adapter and fixture to effect a precise positioning of the fiber end relative to the adapter. The present application incorporates material from disclosure document No. 354,125 filed May 12, 1994, retention of which is respectfully requested.
The use of optical fibers in many applications, such as transmission of coded data, requires testing of the fiber at various check points to ensure transmission integrity. Such testing requires connection of the terminal end(s) of the fiber under test to equipment such as an optical light source and optical power meter. Such test equipment is typically capable of performing very precise measurements and often, for example, in the case of optical time domain reflectometers, quite expensive. Accordingly, it is vital that the fiber under test be connected to the equipment in a manner providing the required precise positional relationships while avoiding damage to the test equipment.
Although various forms of permanent fiber connectors have been employed, extensive time and added cost is involved in their installation. A popular means of temporarily connecting a terminal end of a fiber under test to the test equipment is a device known as a bare fiber adapter. Mechanical connecting means on the bare fiber adapter are releasably affixed-to compatible means on the test equipment as the end portion of the fiber under test is held in the prescribed orientation by the bare fiber adapter. This requires both a proper cleave at the terminal end of the fiber and proper positioning thereof with respect to portions of the bare fiber adapter which mate with the test equipment.
Although technology is presently available for cleaving optical fibers in a manner providing a proper end surface, there remains the problem of ensuring that the fiber end surface is positioned precisely in the desired plane, e.g., flush with the tip of the connector in the bare fiber adapter. Some prior art bare fiber adapters include a polished glass fiber stub permanently secured within the connector portion with one end flush with the tip (or other desired position) and the other end disposed for contact by the end of the fiber under test. This removes the potential of damage to the test equipment by connection thereto of the bare fiber adapter; however, it is virtually impossible to remove any dirt which may enter such adapters, which are therefore classified as non-maintainable, particularly when used in the field.
A frequently used alternative to the bare fiber adapter is the pigtail, i.e., a length of fiber having a permanent, polished surface at one end and a bare (unpolished) surface at the other end. The polished end is connected to the test apparatus and the other end connected to a coupling link or mechanical splice providing direct connection to the fiber to be tested. After the test is completed, the pigtail is re-cleaved and the process repeated. Although pigtails may be reused until they become too short, there are several disadvantages. For example, the cost per number of tests is high when relatively short pigtails are used, but the risk of damage to the pigtail fiber increases proportionately to its length and the added bulk is undesirable. Also, it is necessary to stock or transport many types of pigtails to ensure compatibility with various types of connectors, and connector loses are increased due to the additional mechanical splices.
Accordingly, it is a principal object of the present invention to provide a novel and improved method of positioning and holding a terminal end of an optical fiber at a desired position in a device for connecting the terminal end to test apparatus, or the like.
Another object is to provide a device for use with a bare fiber adapter which ensures precise positioning of the terminal end of an optical fiber in a desired plane of the adapter.
A further object is to provide a novel and improved bare fiber adapter for releasably engaging and holding an end portion of an optical fiber in a desired position.
Still another object is to provide a bare fiber adapter and a compatible stop device useable in combination to position and hold the terminal end of an optical fiber in a desired position relative to the adapter.
In a more general sense, the object of the invention is to provide improved methods and means for positioning and releasably holding an optical fiber in a precise position for optically interfacing the fiber with test apparatus, or other elements.
Other objects will in part be obvious and in part appear hereinafter.